The present invention relates generally to perpendicular recording heads and methods of making same, and more particularly to a perpendicular recording head which minimizes the sensitivity of the head to external applied fields, and which incorporates a magnetoresistive gradiometer for detecting the perpendicular transitions.
Conventional perpendicular recording heads are disclosed in U.S. Pat. No. 4,649,449 entitled "Perpendicular Magnetic Head," issued to Sawada et al., U.S. Pat. No. 4,725,909 entitled "Vertical Magnetic Head Comprising Means for Converging Magnetic Flux to Enable High Density Recording," issued to Kawai, and U.S. Pat. No. 4,807,076 entitled "Thin Film Magnetic Head for Use in Vertical Magnetic Recording" issued to Nakashima et al.
In recording systems that employ perpendicular recording concepts, the orientation of residual magnetization in the recording medium is substantially perpendicular to the surface of the medium. Such perpendicular recording systems have the potential for providing higher recording density than comparable longitudinal recording systems. However, conventional single pole perpendicular recording head designs cause erasure of data recorded in the medium as a result of stray magnetic fields that magnetize the permeable underlayer. The magnetic flux from the underlayer fringes up into the main pole tip and back into the underlayer through the auxiliary pole tip, thus producing a concentrated high field region in the medium just under the narrow thin main pole tip. This high field can cause data erasure or degradation in the recorded data. Also magnetic fields perpendicular to the recording medium can collect on the head and then be concentrated between the main pole tip and the permeable underlayer. Also data erasure at the corners of the recording head is caused by flux in the underlayer that fringes up into one corner of the auxiliary pole and back into the underlayer through another corner. Thus a high field concentration is created under these corners.
The Sawada et al. patent dicusses the disc data erasure problem at column 6, lines 61-66, and a solution to this problem at column 18, line line 46, to column 20, line 63, which describes FIGS. 24-27. In particular, the description with reference to FIGS. 24-27 indicates that two auxiliary poles of the recording head are designed such that one pole is tapered and the other pole has rounded edges. The orientation of the recording head is such that the tapers and rounding of the poles are along the direction of motion of the recording medium. The Nakashima patent discloses a recording head comprising main and auxiliary magnetic poles, and wherein the auxiliary magnetic pole is recessed away from the edge of the main pole by a distance of from 1-5 microns. The Kawai patent discloses a head design wherein two auxiliary poles are placed on the sides of the main pole, transverse to the direction of motion of the recording medium. This design is adapted to minimize external noise related to the storage field effect in the recording medium (see column 4, lines 31-38).
Although a variety of recording heads have been developed, heretofore, no recording head has been developed that minimizes the sensitivity of the head to externally applied fields, and that incorporates a magnetoresistive gradiometer for detecting the perpendicular transitions that experiences minimum fields caused by write coil excitation.